Abstract:

Microcystic adnexal carcinoma (MAC) is a tumor of the sweat gland that occurs on the head and neck. Though the tumor rarely metastasizes, it is locally destructive. The mainstay of treatment has been Mohs surgery or wide local excision with radiotherapy for recurrent disease. In this study, we identified a 50-year-old male who presented with MAC of the right ear that required total right auriculectomy, right temporal bone resection, superficial parotidectomy, neck dissection and free flap reconstruction. H&E staining revealed small rounded neoplastic cells arranged in solid groups and nests with focal lumen formation that diffusely infiltrated the dermis, subcutis and deep soft tissue. There was little stromal response to tumor, but there were many fields with tumor associated inflammation including tumor infiltrating lymphocytes (TILs). We assessed carcinoma expression of PD-L1 and CD8 along with PD-1, LAG-3 and CD8 expression in TILs. Histological analysis showed low levels of PD-L1 expression in MAC, a finding which has not been previously reported. Brisk CD8 positive TILs were also present, suggesting a robust host immune response to the cancer. However, brisk PD-1 and low level LAG-3 expression was also noted in TILs, which indicates suppression of the host anti-tumor immune response. Together, these findings indicate that the use of immunotherapy targeting PD-1/PD-L1 and LAG-3 could augment the anti-tumor response and potentially be used as a neoadjuvant therapy to shrink tumor burden prior to surgery. Due to these cancers occurring in cosmetically sensitive areas, neoadjuvant therapies have the potential to improve aesthetic outcomes after surgery.

Financial Disclosure:
No current or relevant financial relationships exist.

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Saranya Ravi, PhD